Self-watering plant spikes are teardrop-shaped glass devices that make watering while you are away simple. All you must do is fill the bulbs of the devices with water and insert the pointed end into your soil. The bulbs work on the concept of drip irrigation in that they release water as the soil dries. Although you can purchase self-watering plant spikes in a shop, you can make your own using water bottles. Making self-watering plant spikes this way is a good way to recycle plastic water bottles.
Mix a solution containing 237 ml (1 cup) bleach and 2.133 litres (9 cups) hot water to make a 10-percent bleach solution. Wash the water bottle in this solution to completely sterilise it. Rinse the bottles completely before continuing.
Drill a hole in the cap of the bottle with the 1 mm (0.04 inch) diameter drill bit.
Fill the bottle with water. Place the cap on the bottle.
Insert the neck of the bottle into the soil. The water will slowly drain from the hole in the bottle's lid.